Toward a Reliable Synaptic Simulation Using Al-Doped HfO₂ RRAM

Abstract

The potential in a synaptic simulation for neuromorphic computation has revived the research interest of resistive random access memory (RRAM). However, novel applications require reliable multilevel resistive switching (RS), which still represents a challenge. We demonstrate in this work the achievement of reliable HfO 2 -based RRAM devices for synaptic simulation by performing the Al doping and the postdeposition annealing (PDA). Transmission electron microscopy and operando hard X-ray photoelectron spectroscopy results reveal the positive impact of Al doping on the formation of oxygen vacancies. Detailed I−V characterizations demonstrate that the 16.5% Al doping concentration leads to better RS properties of the device. In comparison with the other reported results based on HfO 2 RRAM, our devices with 16.5% Aldoping and PDA at 450 °C show better reliable multilevel RS (∼20 levels) performance and an increased on/off ratio. The 16.5% Al:HfO 2 sample with PDA at 450 °C shows good potentiation/depression characteristics with low pulse width (10 μs) along with a good On/Off ratio (>1000), good data retention at room temperature, and high temperature and good program/erase endurance characteristics with a pulse width of 50 ns. The synapse features including potentiation, depression, and spike time-dependent plasticity were successfully achieved using optimized Al-HfO 2 RRAM devices. Our results demonstrate the beneficial effects of Al doping and PDA on the enhancement of the performances of RRAM devices for the synaptic simulation in neuromorphic computing applications.

Advances of RRAM Devices: Resistive Switching Mechanisms, Materials and Bionic Synaptic Application

“…Compared with conventional silicon-based memory devices like flash memory, it is noted that RRAM devices have demonstrated a series of advantages such as low operation voltage, low power consumption, high density, and enhanced compatibility with traditional complementary metal oxide semiconductor (CMOS) technology [31][32][33]. In addition, with the deepening of research on artificial intelligence (AI) hardware equipment, biomimetic synapse behaviors of RRAM devices have also received extensive attention, which has non-negligible influence in the investigation of electrical artificial synapse [15,17,[34][35][36][37][38].…”

“…Electrode materials like inert metals (Pt and Pd) are always investigated as carrier transportation paths, which have a slight and limited influence on RS performance. Then, electrodes of an RRAM device should have a positive impact on the formation process of CFs, which resulted from the migration of anion, which is always observed in oxygen-vacancy-based RRAM devices [8,9,32]. Finally, the selection of electrode materials for RS medium can directly affect the concentration of migrated anion and accumulated vacancy/cation; proper choice of electrode materials will have a positive influence in the formation process of CFs and also achieve stability enhancement of RRAM device.…”

“…With the development of fabrication methods for electronic devices with thin films, binary metal oxides thin films fabricated by sputtering, ALD (atomic layer deposition) and solution-processed methods have received more interest due to their superior performance. Also, it is indicated that some researchers not only focus on RS layer fabricated with conventional pure binary metal oxides, but also explore effective ways of optimization treatment on metal-oxides-based RS layers, such as stack layers, ionic liquid (IL) process and nanoparticle (NP) doping process, and other similar treatment methods [ 8 , 20 , 32 ].…”

Performance‐Enhanced CsPbBr3/HfO2/Si Heterostructure Optoelectronics through the Tunneling Effect

“…It is deemed to be the most promising gate insulator for replacing SiO 2 in field‐effect transistors (FETs), [ 31,32 ] and it has been applied to fabricate high‐performance electronic devices such as resistive random access memory (RRAM) and capacitors. [ 33–36 ] Additionally, HfO 2 can be used as a refractory material in gate insulation because of its high melting point (2758 °C). [ 37 ] Importantly, the HfO 2 thin film also has good transmittance in the ultraviolet (UV) and infrared (IR) regions, [ 38,39 ] and it can be applied to photodiodes via the tunneling effect.…”

Memristors based on TiOx/HfOx or AlOx/HfOx Multilayers with Gradually Varied Thickness

“…For example, forming-free devices have been demonstrated by metal doping. [8,9] The annealing procedure or the complicated device structure has been adopted for compliance current to prevent the overshoot current. [10,11] Also, multilevel storage capability have been achieved through a bilayer structure.…”